[Sync] Store the past 10 traffic records in memory.

sync/engine/traffic_recorder_unittest.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sync/engine/traffic_recorder.h"
+
+#include "sync/protocol/sync.pb.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace browser_sync {
+
+const unsigned int kMaxMessages = 10;
+const unsigned int kMaxMessageSize = 5 * 1024;
+
+// Ensure the number of records don't exceed |kMaxMessages|.
+TEST(TrafficRecorderTest, MaxRecordsTest) {
+  TrafficRecorder recorder(kMaxMessages, kMaxMessageSize);
+  sync_pb::ClientToServerResponse response;
+
+  for (unsigned int i = 0; i < 2*kMaxMessages; ++i)
+    recorder.RecordClientToServerResponse(response);
+
+  EXPECT_EQ(recorder.records().size(), kMaxMessages);
+}
+
+// Ensure records with size greater than |kMaxMessageSize| are truncated.
+TEST(TrafficRecorderTest, MaxMessageSizeTest) {
+  sync_pb::ClientToServerResponse response;
+
+  sync_pb::ClientToServerResponse::Error* error = response.mutable_error();
+  std::string error_description(kMaxMessageSize * 2, 'a');
+  error->set_error_description(error_description);
+
+  TrafficRecorder recorder(kMaxMessages, kMaxMessageSize);
+  recorder.RecordClientToServerResponse(response);
+
+  TrafficRecorder::TrafficRecord record = recorder.records().front();
+  EXPECT_TRUE(record.truncated);
+  EXPECT_TRUE(record.message.empty());
+}
+
+}  //namespace browser_sync